SF3B1 and myelodysplastic syndrome with ring sideroblasts: In hematologic malignancies, SF3B1 mutations are commonly found in MDS,16, 53 AML, myeloproliferative neoplasms (MPN) and in some MDS/MPN overlap syndromes,54 and in ~10%‐15% of CLL patients.17, 20 Mutations in SF3B1 are specifically enriched in a subtype of MDS previously known as refractory anemia with ring sideroblasts (RARS), characterized by anemia and dysplastic erythroblasts with abnormal iron accumulation in the mitochondria55 causing a “ring” of blue granules to appear around the nucleus upon Prussian blue staining.